Monochromators having a dispersing element such as a diffracting grate which spectrally decomposes the light passing through an entrance slit and having a beam-deflecting element for selecting the wavelength, are known already. Thus, for instance, German patent 37 34 588 describes a monochromator where the diffracting grate is stationary and a beam-deflecting element is rotated with computer control for selecting the wavelength. Such a beam-deflecting element can be, for instance, a revolving mirror or a prism. Stepping motors, a moving coil mechanism, a rotation vibrator, or a motor with trigger mechanism are especially mentioned as a computer-controlled drive for said rotating element. Depending on the efficiency required, the mechanical structure of said rotating elements and the electronic control thereof by means of a computer can be very expensive if a high scanning precision is needed with regard to the frequency range of the light and of the scanning range over the wavelength spectrum.
A simple control of the position and the width of the spectrum is not easily possible.
Therefore, the problem to be solved by the invention is to provide a monochromator for spectrometers which, with a simple structure and at reasonable cost, allows adjustment of the position and the width of the spectrum and also variation of said ranges.